<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		.box{
			width: 520px;
			height: 280px;
			background-image: url("img/5mouse.jpg");
			position: relative;
		}
		.arrow{
			width: 520px;
			position:absolute;
			top:120px;
			overflow: hidden;
			display: none;
		}
		.arrow img:first-child{
			float: right;
			margin-left: -14px;

		}
		.arrow img:last-child{
			float: left;
			margin-left: -14px;
		}
	</style>
</head>
<body>
	<div class="box">
		<div class="arrow">
			<img src="img/arrow-left.png" alt="">
			<img src="img/arrow-right.png" alt="">
		</div>
	</div>
</body>
<script>
	var arr = document.querySelector(".arrow");
	var box = document.querySelector(".box");

	box.onmouseover = function(){
	
		console.log(1);
		arr.style = "display:block";
	}

	box.onmouseout = function(){

		arr.style = "display:none";
	}
</script>
</html>